EN
There exists a universal control sequence ${p̅(m)}_{m=1}^{∞}$ of increasing positive integers such that: Every infinite-dimensional separable Banach space X has a biorthogonal system {xₙ,xₙ*} with ||xₙ|| = 1 and ||xₙ*|| < K for each n such that, for each x ∈ X,
$x = ∑_{n=1}^{∞} x_{π(n)}*(x)x_{π(n)}$
where π(n) is a permutation of n which depends on x but is uniformly controlled by ${p̅(m)} _{m=1}^{∞}$, that is,
$n_{n=1}^{m} ⊆ π(n)_{n=1}^{p̅(m)} ⊆ n_{n=1}^{p̅(m+1)}$ for each m.